Significant progress, highlighted by recent crystallographic structual determinations, has been made in understanding the structure of the polynuclear metal centers in the complex nitrogenase enzyme. The presence of a Mo-Fe-S cluster is known and its ligation within the protein established. Important questions remain that include i) relationship of the FeMoco structure outside of, to that within, the protein; ii) understanding the role of homocitrate and of pH-dependent effects on nitrogenase; iii) determining where and how substrate and inhibitors bind; and iv) establishing highly accurate metrical details for the FeMoco both within and outside the protein. X-ray absorption spectroscopy (both edge and EXAFS) using SR is well-suited to providing insights into electronic and metrical structure of selected atomic sites.